Conventionally, SiC has attracted attention as a material of power devices that can obtain high electric field breakdown strength. As a power device of SiC, for example, a MOSFET, a Schottky diode and the like have been proposed (see, for example, Patent Literature 1).
A power device made of SiC includes a cell portion in which a power element such as a MOSFET or a Schottky diode is formed and a guard ring portion surrounding the periphery of the cell portion. Between the cell portion and the guard ring portion, a connection portion for connecting these portions is arranged. Then, in the outer peripheral region including the guard ring portion, by hollowing the surface of the semiconductor substrate to form a concave portion, a mesa portion provided by protruding the connection portion and the cell portion with an island shape in the thickness direction of the substrate.